title: Regulation of CCN2 gene expression and possible roles in developing tooth germs.
abstract: CCN proteins are extracellular and cell-associated molecules involved in several developmental processes, but their expression patterns and regulation in tooth development remain unclear. Here we first determined the expression patterns of CCN genes in mouse tooth germs. We found that at early stages CCN2 was detected in dental lamina, dental mesenchyme, and primary enamel knot, while other CCN family members were expressed broadly. By the bell stage, all members were expressed in differentiating odontoblasts and ameloblasts, but CCN1 and CCN2 transcripts were conspicuous in differentiating osteoblasts in dental follicle. Next, we asked what signalling molecules regulate CCN2 expression and what roles CCN2 may have. We found that upon surgical removal of dental epithelium CCN2 was not longer expressed in dental mesenchyme in cultured bud stage germs. Implantation of beads pre-coated with BMPs and FGFs onto E12-13 mandibular explants induced CCN2 expression in dental mesenchyme. There was a dose-dependent effect of BMP-4 on CCN2 induction; a concentration of 100 ng/μl was able to induce strong CCN2 expression while a minimum concentration of 25 ng/μl was needed to elicit appreciable expression. Importantly, Noggin treatment inhibited endogenous and BMP-induced CCN2 expression, verifying that CCN2 expression in developing tooth germs requires BMP signalling. Lastly, we found that rCCN2 stimulated proliferation in dental mesenchyme in a dose-dependent manner. Together, the data indicate that expression of CCN genes is spatio-temporally regulated in developing tooth germs. CCN2 expression appears to depend on epithelial and mesenchymal-derived signalling factors, and CCN2 can elicit strong proliferation in dental mesenchyme.
authors.affiliation: Department of Oral and Maxillofacial Rehabilitation, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8525, Japan. Electronic address: kanyama@md.okayama-u.ac.jp.
authors.forename: Manabu
authors.initials: M
authors.lastname: Kanyama
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Shimo
authors.forename: Hiroki
authors.initials: H
authors.lastname: Sugito
authors.forename: Motohiko
authors.initials: M
authors.lastname: Nagayama
authors.forename: Takuo
authors.initials: T
authors.lastname: Kuboki
authors.forename: Maurizio
authors.initials: M
authors.lastname: Pacifici
authors.forename: Eiki
authors.initials: E
authors.lastname: Koyama
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D055511:CCN Intercellular Signaling Proteins / Q000235:genetics* / Q000378:metabolism; D018929:Cell Culture Techniques; D004797:Enzyme-Linked Immunosorbent Assay; D005346:Fibroblast Growth Factors / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D017403:In Situ Hybridization; D059630:Mesenchymal Stem Cells; D051379:Mice; D009805:Odontogenesis / Q000235:genetics* / Q000502:physiology; D014083:Tooth Germ / Q000196:embryology* / Q000378:metabolism
chemical_list: D019485:Bone Morphogenetic Proteins; D055511:CCN Intercellular Signaling Proteins; D005346:Fibroblast Growth Factors
keywords: BMP; CCN; CCN2; FGF; Tooth development